The present invention relates generally to portable fastener driving tools. More specifically, embodiments of the present invention relate to nose assemblies for such tools.
Portable fastener driving tools are typically powered by pneumatic, combustion, electric, or powder systems, and nose assemblies according to embodiments of the present invention are contemplated for use on portable fastener driving tools regardless of the power system. However, exemplary embodiments described herein will refer to combustion-powered tools.
Portable combustion-powered fastener driving tools, such as those manufactured by ITW Paslode under the IMPULSE® brand, and those manufactured by ITW Ramset under the TRAKFAST® brand, are utilized for driving fasteners into workpieces or substrates. An example of a portable combustion-powered fastener driving tool is described in commonly-assigned U.S. Pat. No. 6,164,510, the contents of which are incorporated by reference.
Such tools incorporate a tool housing enclosing a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas called a fuel cell. A battery-powered electronic power control unit produces the spark for ignition. A fan located in a combustion chamber both provides for an efficient combustion within the chamber and facilitates scavenging, including the exhaust of combustion by-products.
The engine includes a reciprocating piston having an elongate, rigid driver blade reciprocating inside a cylinder. A valve sleeve is axially reciprocal about the cylinder and, through a linkage, moves to close the combustion chamber when a work contact element (WCE) at the end of the linkage is pressed against a workpiece or substrate. This pressing action also triggers a fuel metering valve to introduce a specified volume of fuel into the closed combustion chamber.
Upon the pulling of a trigger switch, which causes the ignition of a gas/air mixture in the combustion chamber, the piston and driver blade are driven down the sleeve. Fasteners are fed from a magazine to a nosepiece where they are held in a properly positioned orientation for receiving the impact of the driver blade. A leading end of the driver blade engages a fastener and drives it along a channel defined by the nosepiece into the substrate. The channel is defined by upper and lower guide members of the nosepiece. Next, the piston and driver blade are returned to the original, pre-firing (“ready”) position by differential gas pressures within the cylinder.
The nosepiece and WCE typically include a number of precision parts, the forming and assembly of which can add significantly to the cost of tool production, operation and maintenance. It is desired for these parts to be formed and assembled precisely, for example, to ensure proper alignment and provide a clear path for the driver blade and fastener. Otherwise, jamming of the fastener may result.
Fasteners used with such fastener driving tools include nails designed to be forcibly driven into wood and drive pins designed to be forcibly driven into concrete or masonry. Typically, in such drive pins, the shank has a portion flaring outwardly where the shank adjoins the head. An exemplary use of such drive pins is for attaching metal channels, which are used to mount plasterboard walls, or other metal workpieces to concrete substrates.
Many fastener-driving tools require such fasteners to be fed in strips, in which the fasteners are collated, through magazines having mechanisms for feeding the strips of collated fasteners. Commonly, such fasteners are collated via carriers molded from polymeric materials, such as polypropylene, with individual sleeves, bushings, or holders for the respective fasteners, and with frangible bridges between successive sleeves, bushings or holders.
Specifically, conventional fastener tool nosepieces of the type used with such collated fasteners or drive pins are disclosed in U.S. Pat. No. 6,641,021, which is incorporated by reference, typically include a tubular WCE which extends upward into the nosepiece and includes a laterally opening slot for sequentially receiving collated pins fed from a magazine. In some cases, pins or the molded sleeves carrying the pins become misaligned in the slot and subsequently jam in the WCE.
Additionally, these types of fastener driving tools absorb considerable shock and vibration during and after each actuation (firing). Further, the impact forces generated after fastener driving cause the tool to be propelled away from the fastener as it is driven into the workpiece/substrate. Recently, framing tools have become more powerful to satisfy operator needs. These enhanced forces put large stresses on many parts of the tool, which may cause more rapid wear of the nosepiece and/or the WCE. Extended wear to the nosepiece also may cause the tubular WCE to break or warp. Besides the cost of repair, such malfunctions result in tool downtime, which is exacerbated by the relatively complex nosepiece assembly.
Another design factor in such tools is that upon ignition of the gas/air mixture in the combustion chamber, at the beginning of the fastener driving cycle, recoil forces often cause the tool to lift from the workpiece. In some cases, this recoil causes fasteners to be improperly or inaccurately placed. In other cases, the movement of the tool after ignition impedes accurate placement of subsequent fasteners.
Thus, there is a need for an improved nose assembly for a portable fastener driving tool that addresses one or more of the above-identified design issues of production and assembly cost, required precision for assembly, and maintenance and repair costs. In addition, there is a need for an improved nose assembly for a fastener driving tool that addresses the problem of tool lift during the fastener driving cycle.